Is there a quick way to set a specific length for multiple edges?
Scale Pivot Center to 3D Cursor, Snap Cursor to selection for your convenience






The scale pivot is set to cursor. Please see tooltip in the image above.  An axis is decided such as [X]
We are using the yellow mesh in edit mode for this example.
Two vertices are selected on axis extreme .. left in this example ... Snap Cursor to Selected Shift S Cursor to Selected.  Now we can scale to the leftmost and increment from the leftmost in this example. See the cursor in the image above. It can act as the [X] zero of our imaginary ruler.
Select the vertex loop 1 in question.  Scale vertices on X axis to 0.


sx0

Grab on axis. Specify exact dimension.  


gx.75.  I used [.75] for this example.

Select the vertex loop 2 in question.  Scale vertices on X axis to 0.


sx0

Grab on axis. Specify exact dimension.  


gx1.5.  [.75] increment in relation to previous vertex
loop for this example.  If I had again set the cursor to the previous vertex loop I could have used a [.75] value as in gx.75





In the image above the Mesh Display shows edge length confirming our actions.


Of course you can snap the cursor to a single vertex or collection of vertices when the need suits you.  The cursor is to serve at your pleasure.
The info window on top shows some actions.  Selection is not shown.
You may also investigate vertex slide.  Vertex Slide is not shown here.
Assuming rectilinear alignment on the global XYZ coordinate system.  When this is not the case Blender allows you to create an [orientation] so the displacement vector can point in any direction. Please inspect, verify and improve these suggestions.